The present invention relates generally to fastener-driving tools used to drive fasteners into workpieces, and specifically to combustion-powered fastener-driving tools, also referred to as combustion tools.
Combustion-powered tools are known in the art, and one type of such tools, also known as IMPULSE® brand tools for use in driving fasteners into workpieces, is described in commonly assigned patents to Nikolich U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474; 4,403,722; 5,197,646; 5,263,439 and 6,145,724, all of which are incorporated by reference herein. Similar combustion-powered nail and staple driving tools are available commercially from ITW-Paslode of Vernon Hills, Ill. under the IMPULSE®, BUILDEX®□ and PASLODE® brands.
Such tools incorporate a tool housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces a spark for ignition, and a fan located in a combustion chamber provides for both an efficient combustion within the chamber, while facilitating processes ancillary to the combustion operation of the device. Such ancillary processes include: inserting the fuel into the combustion chamber; mixing the fuel and air within the chamber; and removing, or scavenging, combustion by-products. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a single cylinder body.
The combustion engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a cylinder body. A valve sleeve is axially reciprocable about the cylinder and, through a linkage, moves to close the combustion chamber when a workpiece contact element (WCE) at the end of the linkage is pressed against a workpiece. This pressing action also triggers a fuel metering valve to introduce a specified volume of fuel into the closed combustion chamber.
Upon the pulling of a trigger switch, which causes the spark to ignite a charge of gas in the combustion chamber of the engine, the combined piston and driver blade is forced downward to impact a positioned fastener and drive it into the workpiece. The piston then returns to its original, or pre-firing position, through differential gas pressures within the cylinder. Fasteners are fed magazine-style into the nosepiece, where they are held in a properly positioned orientation for receiving the impact of the driver blade.
In many types of combustion tools, the WCE includes a pusher rod which reciprocates with the WCE relative to a nosepiece fixed to the tool. As the tool is depressed against the workpiece, causing movement of the WCE relative to the tool nosepiece, an upper end of the pusher rod impacts a cage assembly, which is ultimately connected to the valve sleeve. To reduce impact damage to the cage assembly through repeated use, a rubber-like grommet was placed at the impact point of the pusher rod. Disadvantages of that arrangement included that the grommet deteriorated relatively quickly compared to the useful life of the tool, and that the shock-absorbing function of the grommet resulted in inefficiency through lost motion and extra play in the system.
Thus, there is a need for a cage and probe assembly for a combustion-powered fastener-driving tool which addresses the drawbacks of the prior art.